@black_falcon120: first question - are you trolling? If not, please continue reading.
1) First, and most importantly - you absolutely *must* fit modules etc. to all your ships (for advice on builds i.e. what to put on what: http://wiki.wargaming.net/en/World_of_Warships ) The wiki will also give you some indication as to what each ship is for e.g. Bismark (and Tirpitz) are absolutely not snipers, and so on.
2) If you can't afford the silver to buy/mount the relevant modules, play more at lower tiers (against real people) to generate the silver - you simply have to be patient (or buy premium account etc.).
3) Without the modules you are a liability to your team-mates; deliberately gimping yourself is simply unethical, so don't do it.
With that out of the way, some thoughts on your original question:
As others have said, until you get better (and/or can afford to mount a full module build), I would suggest avoiding T8 premiums - you will regularly face T10 opponents, most of them with a decent captain (read up on captain skills etc. if you haven't already), and *all* of them fully built out with modules etc.
I would suggest spending your money on several T6-7 premiums (if you have a one-shot voucher, perhaps look at those you can get from the tech tree, and buy the relevant doubloons in one hit); I would also suggest they be whatever class you do best with (and actually like playing) - the best earners are those you don't suck in, and actively want to play multiple times. e.g. I use my DDs a lot, as that's the class I suck least with, and I hardly play (say) my Alabama as I'm really not good at BBs.
Read/watch multiple reviews (LWM - linked to from the wiki is a good start), to try and avoid buying too many turkeys (see previous point about needing things you want to play).
Oh yes, take WG's marketing blurb with an enormous bucket of salt - they will try and persuade you that every premium is awesome, when this is not entirely the case.